A conventional floating-piston accumulator has a housing tube and a filling conduit with a filling attachment which are arranged separate from each other on a cover on the accumulator housing end. The conventional arrangement requires two separate bores or holes in the cover. The switch member comprises a magnet, while the sensor is a Reed relay ("Hydropneumatic Floating-Piston Accumulator", Brochure No. 3.301.6/9.82 of Gesellschaft fuer Hydraulik-Zubehoer mbH)